What is it?

Horsetail is a plant. The above ground parts are used to make medicine.

Horsetail is used for “fluid retention” (edema), kidney and bladder stones, urinary tract infections, the inability to control urination (incontinence), and general disturbances of the kidney and bladder.

There have been reports of horsetail products being contaminated with a related plant called Equisetum palustre. This plant contains chemicals that can poison cattle, but toxicity in people has not been proven.

How does it work?

The chemicals in horsetail may have antioxidant and anti-inflammatory effects. Plants related to horsetail contain chemicals that work like "water pills" (diuretics) and increase urine output. But it isn't clear whether horsetail has this effect.

Are there safety concerns?

Horsetail is POSSIBLY UNSAFE when taken by mouth long-term. It contains a chemical called thiaminase, which breaks down the vitamin thiamine. In theory, this effect could lead to thiamine deficiency. Some products are labeled "thiaminase-free," but there is not enough information available to know if these products are safe.

Special precautions & warnings:

Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking horsetail if you are pregnant or breast-feeding. Stay on the safe side and avoid use.

Alcoholism: People who are alcoholics are generally also thiamine deficient. Taking horsetail might make thiamine deficiency worse.

Diabetes: Horsetail might lower blood sugar levels in people with diabetes. Watch for signs of low blood sugar (hypoglycemia) and monitor your blood sugar carefully if you have diabetes and use horsetail.

Low potassium levels (hypokalemia): Horsetail might flush potassium out of the body, possibly leading to potassium levels that are too low. Until more is known, use horsetail with caution if you are at risk for potassium deficiency.

Low thiamine levels (thiamine deficiency): There is a concern that horsetail could make thiamine deficiency worse.

Are there interactions with medications?

Moderate

Be cautious with this combination.

Lithium

Horsetail might have an effect like a water pill or "diuretic." Taking horsetail might decrease how well the body gets rid of lithium. This could increase how much lithium is in the body and result in serious side effects. Talk with your healthcare provider before using this product if you are taking lithium. Your lithium dose might need to be changed.

Large amounts of horsetail might decrease potassium levels in the body. "Water pills" can also decrease potassium in the body. Taking horsetail along with "water pills" might decrease potassium in the body too much.

Are there interactions with herbs and supplements?

Horsetail and areca both reduce the amount of thiamine that the body has to use. Using these herbs together raises the risk that the amount of thiamine will become too low.

Chromium-containing herbs and supplements

Horsetail contains chromium (0.0006%) and could increase the risk of chromium poisoning when taken with chromium supplements or chromium-containing herbs such as bilberry, brewer's yeast, or cascara.

Herbs and supplements that might lower blood sugar

Horsetail might lower blood sugar. Using it along with other herbs and supplements that have the same effect might cause blood sugar to drop too low in some people. Some of these products include alpha-lipoic acid, bitter melon, chromium, devil's claw, fenugreek, garlic, guar gum, horse chestnut, Panax ginseng, psyllium, Siberian ginseng, and others.

Thiamine

Crude horsetail contains thiaminase, a chemical that breaks down thiamine. Cattle that eat a lot of horsetail have developed thiamine deficiency.

Are there interactions with foods?

What dose is used?

The appropriate dose of horsetail depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for horsetail. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

This copyrighted, evidence-based medicine resource is provided by Natural Medicines Comprehensive Database Consumer Version. Natural Medicines Comprehensive Database disclaims any responsibility related to consequences of using any product. This monograph should not replace advice from a healthcare professional and should not be used for the diagnosis or treatment of any medical condition.